diseases with one another, and if you're close enough to sell someone a newspaper, you're close enough to rob them as well. from the course of, over the course of history, cities have been battling with the demons of density; crime, contagious disease, congestion. this is a map a of death rates in new york from 1800 to today. a boy born in new york city could expect to live seven years less than the national average, today life expectancies are three years longer. we don't understand fully why cities like boston and new york are healthier than denser areas. some people credit walking, more people credit social connection. among younger people, though, it's crystal clear. two big causes for the death, motor vehicle accidents and suicide, both much rarer. it's a lot safer to get on the t after a few drinks than it is to get behind the wheel of a car. not that i'm recommending anything. [laughter] maybe suicide rates also reflect social connection or the influence of gun culture where there's a strong existence. now, this didn't happen by accident. america's cities and towns only became safe thr